(199h) Genome-Scale Flux Balance Analysis of Tree Metabolism

Photoautotrophic organisms are important sources for the production of renewable fuels and chemicals. Plants and trees form a subset of such organisms with unique properties and complex metabolism. Plant metabolism is much more complex than that of prokaryotes and other eukaroyotes with cellular compartmentation and replication of pathways in multiple compartments. Furthermore, trees exhibit interesting features like efficient usage of their nitrogen reserves via recycling to specialized storage proteins and generation of hydrocarbons to deal with heat stress. In plants, a few pioneering studies have applied flux balance analysis (FBA) for estimating fluxes using plant cell culture (Belau et al, Plant Physiol. 149: 585-598, 2009; Williams et al, Plant Physiol. 154: 311-323, 2010; Hay et al, The Plant Journal, 67(3): 513–525, 2011). The metabolism of trees has not been well studied compared to that of model plants such as Arabidopsis and maize.  

This presentation will report an investigation of metabolism in a model tree using genome-scale FBA. We have reconstructed a genome scale model of a model tree using reactions from the BioCyc family of database. As part of the study, we will use FBA for estimating fluxes in the tree using previously determined biomass compositions, thus obtaining flux distributions on a genome scale. We will then estimate the flux distributions under a set of interesting and physiologically relevant conditions. We will investigate flux distributions for minimizing production of lignin to improve viability of the tree as a biofuel crop; maximizing production of nitrogen storage proteins to elucidate underlying fluxes during seasonal nitrogen cycling; and flux changes during biosynthesis of the hydrocarbon isoprene, whose production by trees impacts atmospheric chemistry. These studies will represent the first application of genome scale FBA to a model tree system, and additionally provide insight on the metabolic network in model tree organisms.